I used to not think something like Minato asking Sakura if she was Naruto's girlfriend would happen the way it did, if even at all. I didn't even think a NaruSaku/MinaKushi confirmation would happen by Minato comparing Sakura to Kushina. I still remember clearly saying that that wasn't going to happen in 631 the day before it was released. And then I ended up hilariously and satisfying wrong.
I've seen some NH fans on tumblr getting saying it didn't make sense that Minato asked a question like that to Sakura and arguing "He doesn't even know his son! He doesn't know their relationship! He's a bad source for NS!". Basically just typical raging, but I can agree that was pretty out of left field how that scene happened.
I don't think Minato's an unreliable source tho. Wasn't his spirit inside Naruto right up until the Pain Arc? He said he already knew what happened to Jiraiya and everything that was happening. Maybe he asked if Sakura was Naruto's girlfriend because he saw something between them while he was inside Naruto. Or am I completely misinterpreted the Pain Arc exchange?